JP2575045Y2 - AC power loss detection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an AC power supply disconnection detection circuit that detects that power supply from an AC power supply to a load is cut off.

[Conventional technology]

When a heat source device such as a burner is driven by an AC power supply as a load, a protection device such as a thermal fuse or a thermostat is generally connected in series to a power supply line, and when an overload or the inside of the device is heated, the protection device is activated. The supply of AC power to the load is cut off to protect the load.

And as a circuit for detecting such a cutoff state,
Conventionally, there is one shown in FIGS.

First, in FIG. 3, an AC power supply of 100 V AC is connected to the heat source equipment 1 via a power supply line l, a fuse 2 is inserted in the power supply line l in series, and a lamp L is connected to the fuse 2 in parallel. ing. Therefore, when the fuse 2 is blown and the AC power is cut off at the time of an overload or the like, the AC power of 100 V is applied to the lamp L, whereby the lamp L is turned on to indicate that the lamp L is cut off.

In FIG. 4, a relay RL is connected in parallel with the fuse 2, and its output is connected to the control circuit 5. Therefore, when the fuse 2 is blown, AC100V is applied to the relay RL, thereby energizing the relay RL and closing the contact, so that the control circuit 5 detects this state and turns on a display lamp (not shown) or a heat source. The device 1 is controlled.

[Problems to be solved by the invention]

Those described above for Figure 3 and Figure 4, although the fuse 2 is one, as shown in FIG. 5 and FIG. 6, the fuse 2 ₁ to the power supply line l, 2 _2, 2 ₃ (hereinafter 2 _n ) are connected in series, and each fuse 2 _n has a lamp L ₁ , L ₂ , L ₃
(Hereinafter L referred _n) or relay _{RL 1, RL 2, RL 3} ( hereinafter RL _n
Considering the case where one of the fuses 2 _n is blown, the corresponding lamp Ln or the relay _Ln or the relay Ln, as is apparent from the operation of FIGS.
There is no problem because RL _n is turned on and driven.
If a plurality of fuses _2n provided in each section are blown at the same time so that overheating of each section can be detected in an identifiable manner, the following problem occurs.

That is, those of FIG. 5, since the applied voltage of each lamp L _n is decreased, the lighting becomes unstable, and in some cases it may not light up. Also, by way of FIG. 6, the voltage applied to the relay RL _n is lowered, the operation of the contact point becomes unstable, sometimes it said contact does not close. Generally, the relay is expensive and large, so that the equipment becomes expensive and the size becomes large.

Therefore, the present invention provides an AC power supply disconnection detection circuit that can reliably detect the interruption of the AC power supply even when a plurality of protective means such as fuses connected in series to the power supply line are simultaneously activated. That is the task.

[Means for solving the problem]

To solve the above-mentioned problems, the AC power supply disconnection detection circuit made by the present invention protects the load by cutting off the AC power supply to the load by cutting off the power supply line connecting the AC power supply and the load due to overload or overheating. A plurality of protection means are connected in series, and one of the protection means is blown to shut off AC power so that no AC power is supplied to the load, and is connected in parallel with each of the protection means. A rectifying unit that rectifies and outputs an AC power applied when the protection unit is blown, an LED that emits light driven by the rectified output of the rectifying unit, and a switching element that is turned on by the light emitted by the LED. And a cut-off of the AC power supply is detected by an ON output of the photocoupler.

[Action]

In the above configuration, when the protection means is not blown, the protection means short-circuits the rectifier means, so that the rectification means does not rectify the AC power supply and has no rectified output. The power is rectified and the rectified output is supplied to the photocoupler. Therefore, the photocoupler LED
Is driven by this rectified output to emit light, and this LED
The switching element of the photocoupler is turned on by the light emitted from the photocoupler, and the cutoff state of the AC power supply is detected by the on output of the photocoupler.

At this time, the rectifier and the photocoupler are respectively connected in parallel to each of the plurality of protective units connected in series to the power supply line. Although the rectified output decreases, the LED of the photocoupler has a wide operating range with respect to the input current, and can be driven reliably with a small DC current to emit light.
The interruption state of the AC power supply can be reliably detected.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of an AC power supply disconnection detecting circuit according to the present invention, in which the same reference numerals are given to the same parts as those described above with reference to FIGS. 3 to 6. .

Rectifier circuits 3 ₁ , 3 ₂ , 3 ₃ (hereinafter referred to as 3 _n ) are connected in parallel to each fuse 2 _n, and the rectified outputs of the fuses 2 _n are connected to current limiting resistors R ₁₁ , R ₁₂ , R ₁₃ (hereinafter referred to as R _1n ). Connected to the photocouplers 4 ₁ , 4 ₂ , 4 ₃ (hereinafter referred to as 4 _n ), respectively.
The output of each photocoupler 4 _n is input to the control circuit 5.

As is well known, the photocoupler 4 _n includes LEDs D ₁ , D ₂ , D ₃ (hereinafter referred to as D
_n ) and phototransistors Q ₁ , Q ₂ , Q ₃ (hereinafter referred to as Q _n ) which are turned on by the light emitted from the LEDD _n .

In the above configuration, when all the fuses 2 _n not actuated (blown), the both ends of each commutation circuit 3 _n because no voltage is applied, the rectified output is 0V. Thus since the the LED D _n of the photo-coupler 4 _n no current flows, the phototransistor Q _n is in the OFF state.

On the other hand, when the one of the fuse 2 _n has been blown, since the opposite ends of the corresponding rectifier circuit 3 _n AC100V is applied, the rectifier circuit 3 _n rectifies AC100V, the photocoupler 4 _n connected to the output a DC voltage is applied through a resistor R _1n current limit to the LED D _n. This emits a current flows in the LED D _n, since the phototransistor Q _n is turned on by receiving the light, the control circuit 5 performs lighting and control of the heat source apparatus 1 of the display lamp to detect this condition.

Further, when the fuse 2 _n is blown plurality at the same time, reduces the voltage across the rectifier circuit 3 _n, rectified DC voltage also decreases. However, the LEDD _{n of the} photocoupler 4 _{n has} a wide operating range with respect to its input current, for example, generally about 1 mA to 50 mA.Therefore, by setting the current limiting resistor R _1n to a predetermined value, the rectifier circuit 3 _n the LED D _n even when the DC voltage is low from the sufficient current is supplied to the light emitting.

Thus, a plurality of the LED D _n corresponding to the blown fuse 2 _n
There emitted simultaneously, each phototransistor Q _n can be reliably turned on, the control circuit 5 based on the output of the photo transistor Q _n can detect the cut-off state.

Figure 2 is a circuit diagram showing a specific example of the rectifier circuit 3 _n in FIG. 1, each of which forms a half-wave rectifier circuit by the rectifier diode D, resistors R _1, R ₂ capacitor C.

〔effect〕

As described above, according to the present invention, a plurality of protection means provided in each part so that fusing due to overload or overheating can be detected in an identifiable manner, are connected in series to a power supply line connecting an AC power supply and a load, If a plurality of these protection means are blown at the same time, the rectification output of the rectification means connected in parallel with the blown protection means is reduced, but is reliably supplied to each photocoupler, and furthermore, the LED of the photocoupler is responsive to the input current. Since the operating range is wide and light can be reliably driven and driven by a small DC current, the cutoff state of the AC power supply can be reliably detected.

In addition, the size of the device can be reduced, and the device can be configured at low cost.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of an AC power supply disconnection detection circuit according to the present invention, FIG. 2 is a circuit diagram showing a specific example of a part of the circuit of FIG. 1, and FIGS. FIG. 3 is a circuit diagram illustrating a configuration example of a power-off detection circuit. 1 ... load (heat source device), 2,2 _1, 2 _2, 2 ₃ ... protection (fuse), 3 _1, 3 _2, 3 ₃ ... rectifying means (rectifier circuit), 4 _1, 4 _2,
4 ₃ … Photocoupler, 5… Control circuit, l… Power supply line.

Claims (1)

(57) [Scope of request for utility model registration] 1. A power supply line connecting an AC power supply and a load,
A plurality of protection means are connected in series to protect the load by fusing due to overload or overheating and cutting off the supply of AC power to the load, and by blowing one of the protection means, the AC power supply is cut off and AC is applied to the load. A rectifier connected in parallel with each of the protection means, for rectifying and outputting an AC power applied when the protection means is blown, and a rectification output of the rectifier. LED that emits light when driven
An AC power supply disconnection detection circuit, comprising: a photocoupler including a switching element that is turned on by light emitted by the ED, and detecting the interruption of the AC power supply based on an ON output of the photocoupler.